Detection of nitric oxide is of great importance in a number of bio-medical applications such as non-invasive medical diagnostics based on exhaled human breath analysis or study of the regulation of biological and physiological processes in human and mammalian cells. None of currently available NO sensing technologies can simultaneously provide sub-parts-per- billion sensitivity, <0.1-sec time resolution, capability of selective measurements of NO isotopes, no sample preparation, and high immunity to interferences from other molecular species in a single, compact, portable and user-friendly instrument. The research proposed in this project will lead to development of a novel laser spectroscopic sensing instrumentation, which will provide unique capabilities of biogenic NO quantification. The new technology will be based on Faraday rotation spectroscopy, which can provide unprecedented sensitivity and specificity to NO. To achieve the goals for the system performance and a compact footprint a novel sensitivity enhancement based on ultra-sensitive optical heterodyne detection will be implemented. A broadly tunable mid-infrared external cavity quantum cascade laser will be used as a spectroscopic source, which will provide capability of quantification of all stable NO isotopes with a single instrument. The specific aims of the proposed project are: 1. Development and laboratory demonstration of a novel laser based, optical heterodyne Faraday rotation spectroscopic system for detection of all stable isotopes of NO in exhaled human breath with sub-ppb sensitivity, sub-second resolution and high specificity to discriminate against potentially interfering gases, particularly H2O and CO2. 2. Development, laboratory tests and implementation of reliable consumable-free calibration techniques, which will provide automatic and maintenance-free operation of the instrument. 3. Design and prototype development of a portable sensing instrument with sensitivity, selectivity and fast response time required for exhaled NO concentration measurements in both single breath maneuver as well as during tidal breathing. The technology developed during this project will be broadly applicable to breath analysis as well as other bio-medical applications. In addition other non-biomedical applications such as atmospheric pollution monitoring, combustion diagnostics and vehicle exhaust monitoring that indirectly but significantly help improving people's health will benefit from the proposed development of laser based gas analyzer technology. PUBLIC HEALTH RELEVANCE: Project Narrative Nitric oxide plays a major role in a number of biological processes such as indication of airway inflammation, regulation of blood pressure, regulation of fundamental cellular activities such as whether cells live or die, or can even change the computational ability of the brain. Therefore better understanding of the mechanisms by which nitric oxide contributes to the process biology and bio-chemistry can significantly enhance understanding of many types of diseases or injuries and will result in improved detection, prevention or treatment methods. The proposed research will provide doctors and scientists with a novel nitric oxide sensing instrumentation that will outperform technologies currently used in clinical studies, and will allow for significant advancements in bio-medical science and for improvements of public health.